Regional differences of fat depot attenuation using non-contrast, contrast-enhanced, and delayed-enhanced cardiac CT

Associations between the serum triglyceride-glucose index and pericoronary adipose tissue attenuation and plaque features using dual-layer spectral detector computed tomography: a cross-sectional study

Background and aims

The triglyceride-glucose (TyG) index is a reliable alternative marker for insulin resistance (IR). Pericoronary adipose tissue (PCAT) can indirectly reflect coronary inflammation. IR and coronary inflammation play a key role in the development and progression of coronary atherosclerosis. Therefore, this study investigated the relationships between the TyG index, PCAT and atherosclerotic plaque characteristics to explore whether IR might lead to coronary artery atherosclerosis progression by inducing coronary inflammation.

Methods

We retrospectively collected data on patients with chest pain who underwent coronary computed tomography angiography using spectral detector computed tomography at our institution from June to December 2021. The patients were grouped based on their TyG index levels: T1 (low), T2 (medium), and T3 (high). Each patient was assessed for total plaque volume, plaque load, maximum stenosis, the plaque component volume proportion, high-risk plaques(HRPs), and plaque characteristics (including low attenuation plaques, positive remodeling, a napkin ring sign, and spot calcification). PCAT quantification was performed on the proximal right coronary artery using the fat attenuation index (FAI) measured from a conventional multicolor computed tomography image (FAI_120kVp), a spectral virtual single-energy image (FAI_40keV), and the slope of the spectral HU curve (λ_HU).

Results

We enrolled 201 patients. The proportion of patients with maximum plaque stenosis, positive remodeling, low-density plaques, and HRPs increased as the TyG index level increased. Moreover, the FAI_40keV and λ_HU significantly differed among the three groups, and we identified good positive correlations between FAI_40keV and λ_HU and the TyG index (r = 0.319, P <0.01 and r = 0.325, P <0.01, respectively). FAI_120kVp did not significantly differ among the groups. FAI_40keV had the highest area under the curve, with an optimal cutoff value of -130.5 HU for predicting a TyG index value of ≥9.13. The multivariate linear regression analysis demonstrated that FAI_40keV and λ_HU were independently positively related to a high TyG index level (standardized regression coefficients: 0.117 [P <0.001] and 0.134 [P <0.001], respectively).

Conclusions

Patients with chest pain and a higher TyG index level were more likely to have severe stenosis and HRPs. Moreover, FAI_40keV and λ_HU had good correlations with the serum TyG index, which may noninvasively reflect PCAT inflammation under insulin resistance. These results could help explain the mechanism of plaque progression and instability in patients with insulin resistance might be related to IR-induced coronary inflammation.

Accuracy of a CT density threshold enhancement in distinguishing pancreas parenchymal necrosis in cases of acute pancreatitis in the first week

PURPOSE

The purpose of this study was to identify attenuation threshold value on computed tomography (CT) that allowed discriminating between interstitial edematous pancreatitis (IEP) and necrotizing pancreatitis (NP) in patients with acute pancreatitis during the first week of the disease and evaluate interobserver reproducibility for the diagnosis of acute pancreatitis category.

MATERIALS AND METHODS

Patients with acute pancreatitis who underwent CT examination of the abdomen between March 2015 and December 2019 were retrospectively included. Actual diagnosis of IEP or NP was based on final clinical report, follow-up evaluation, and complications. Six regions of interest were manually placed in the pancreatic gland and peripancreatic fat, and differences in CT attenuation values before contrast injection and during the portal venous phase of enhancement were computed. Performance in the diagnosis of AP category was evaluated using receiver operating characteristic analysis. Interobserver agreement was estimated by the intraclass correlation coefficient (ICC) and Bland Altman analysis was used to estimate reproducibility between pairs of observers.

RESULTS

Sixty-six patients with NP (46 men, 20 women; mean age, 55 ± 17 [SD] years; age range: 20-89 years) and 70 patients with IEP (39 men, 31 women; mean age, 54 ± 18 [SD] years; age range: 21-87 years) were included. An enhancement value less than 30 Hounsfield units (HU) in the pancreatic gland during the portal phase compared to non-contrast phase, yielded 90.9% sensitivity (60/66; 95% CI: 81.3-96.6), 94.3% specificity (66/70; 95% CI: 86.0-98.4) and an area under curve of 0.958 (95% CI: 0.919-0.996) for the diagnosis of NP versus IEP. Interobserver reproducibility for pancreas enhancement was good using Bland Altman plot and ICC was excellent for pancreatic gland analysis (ICC 0.978; 95% CI: 0.961-0.988) but poor or moderate (ICC ≤0.634) regarding peripancreatic fat necrosis.

CONCLUSION

By using a pancreas enhancement threshold value of 30 HU, CT is accurate and reproducible for the diagnosis of NP during the first week of the disease.

Pericoronary fat attenuation index in computed tomography angiography is associated with mortality in end-stage renal disease

Background

An increased pericoronary fat attenuation index (FAI) on computed tomography angiography (CTA) is associated with increased all-cause and cardiac mortality in the general population. However, the ability of pericoronary FAI to predict long-term outcomes in chronic kidney disease (CKD) patients is unknown.

Methods

In this single-center retrospective longitudinal cohort study, we assessed the utility of CTA-based pericoronary FAI measurement to predict mortality of CKD patients, including those with end-stage renal disease (ESRD). Mapping and analysis of pericoronary FAI involved three major proximal coronary arteries. The prognostic value of pericoronary FAI for long-term mortality was assessed with multivariable Cox regression models.

Results

Among 268 CKD participants who underwent coronary CTA, 209 participants with left anterior descending artery (LAD) FAI measurements were included. The pericoronary FAI measured at the LAD was not significantly associated with adjusted risk of all-cause mortality (hazard ratio [HR], 2.08; 95% confidence interval [CI], 0.94–3.51) in any CKD group. However, ESRD patients with elevated pericoronary FAI values had a greater adjusted risk of all-cause mortality compared with the low-FAI group (HR, 2.26; 95% CI, 1.11–4.61).

Conclusion

The pericoronary FAI measured at the LAD predicted long-term mortality in patients with ESRD, which could provide an opportunity for early primary intervention in ESRD patients.

Dual-layer spectral detector CT to study the correlation between pericoronary adipose tissue and coronary artery stenosis

BACKGROUND

To investigate the relationship of pericoronary adipose tissue (PCAT) with coronary artery stenosis using dual-layer spectral detector CT (SDCT).

METHODS

99 patients were retrospectively divided into normal group, non-significant stenosis group and significant stenosis group (n = 33 in each group). Fat attenuation index (FAI) 40kev, spectral curve slope (λHU), effective atomic number (Eff-Z) and epicardial fat volume (EFV) were quantitatively evaluated of the narrowest part of the lesion tissue by SDCT.

RESULTS

There were significant differences in PCAT parameters on SDCT (FAI40keV, λHU, Eff-Z and EFV) among the three groups (P < 0.05). FAI40keV, λHU, and Eff-Z in significant stenosis group were statistically different from those in normal group and non-significant stenosis group (P < 0.05). FAI40keV, λHU, and Eff-Z in non-significant stenosis group were statistically different from significant stenosis group (P < 0.05). EFV in normal group were significantly lower in non-significant stenosis group and significant stenosis group (P < 0.001). Univariate and multivariate logistic regression analyses identified FAI40keV (OR = 1.50, 95%CI 1.01 to 1.09) and λHU (OR = 6.81, 95%CI 1.87 to 24.86) as independent predictors of significant stenosis. FAI40keV and λHU had quite good discrimination, with an AUC of 0.84 and 0.80 respectively.

CONCLUSION

FAI40keV, λHU, and Eff-Z on SDCT in significant stenosis group were significantly different from normal and non-significant stenosis group while EFV in normal group were significantly different from non-significant stenosis group and significant stenosis group. FAI40kev and λHU were risk factors for significant stenosis.

Association of Pericoronary Adipose Tissue Quality Determined by Dual-Layer Spectral Detector CT With Severity of Coronary Artery Disease: A Preliminary Study

Background: Pericoronary adipose tissue (PCAT) is considered as a source of inflammatory mediators, leading to the development of coronary atherosclerosis. The study aimed to investigate the correlation between PCAT quality derived from dual-layer spectral detector CT (SDCT) and the severity of coronary artery disease (CAD), and whether PCAT parameters were independently associated with the presence of CAD.

Materials and Methods: A total of 403 patients with symptoms of chest pain who underwent SDCT were included. PCAT quality including fat attenuation index (FAI) measured from conventional polychromatic CT images (FAI_120kvp) and spectral virtual mono-energetic images at 40 keV (FAI_40keV), slope of spectral HU curve (λ_HU), and effective atomic number (Eff-Z) were measured around the lesions representing the maximal degree of vascular stenosis in each patient. Meanwhile, overall epicardial adipose tissue (EAT) attenuation was acquired in the conventional polychromatic energy imaging.

Results: FAI_40keV, λ_HU, Eff-Z, and FAI_120kvp increased along with the degree of CAD in general and were superior to the overall EAT attenuation for detecting the presence of CAD. Multivariate logistic regression analysis indicated that FAI_40keV was the most powerful independent indicator (odds ratio 1.058, 95% CI 1.044–1.073; p < 0.001) of CAD among these parameters. Using an optimal cut-off (−131.8 HU), FAI_40keV showed higher diagnostic accuracy of 80.6% compared with the other parameters.

Conclusions: These preliminary findings suggest that FAI_40keV on SDCT may be an appealing surrogate maker to allow monitoring of PCAT changes in the development of CAD.

Pericoronary adipose tissue attenuation assessed by dual-layer spectral detector computed tomography is a sensitive imaging marker of high-risk plaques

Background

The pericoronary fat attenuation index (FAI) derived from conventional polychromatic computed tomography (CT) can capture the presence of coronary inflammation. However, conventional polychromatic CT has limitations in material component differentiation, and spectral CT could have a better ability to discriminate tissue characteristics. Hence, this study sought to assess pericoronary adipose tissue (PCAT) attenuation using spectral CT and explore its association with atherosclerotic plaque characteristics.

Methods

We enrolled 104 patients with coronary atherosclerosis who met the inclusion criteria and underwent coronary CT angiography with dual-layer spectral detector computed tomography (SDCT). Plaque anatomical characteristics were measured, and the PCAT attenuation was assessed by polychromatic images (CT_poly), virtual mono-energetic images at 40 keV (CT_{40 keV}), the slope of spectral attenuation curve (λ_HU), and the effective atomic number (Z_eff). The association of PCAT attenuation indicators with the presence of high-risk plaques was analyzed, along with the indicators' ability to identify high-risk plaques.

Results

PCAT attenuation indicators around high-risk plaques were higher than those around non-high-risk plaques, especially CT_{40 keV} [-153.76±24.97 (non-high-risk plaque) vs. -119.87±22.74 (high-risk plaque), P<0.001]. CT_{40 keV} was a predictive factor of high-risk plaques, and high CT_{40 keV} (≥-120.60 HU) could assist in the identification of high-risk plaques, with an area under the curve of 0.883 (95% CI: 0.83-0.94, P<0.05).

Conclusions

PCAT surrounding high-risk plaques showed higher attenuation; a finding that has been associated with coronary artery inflammation. The metrics derived from SDCT, especially CT40 _keV, showed higher discriminatory power for detecting changes in PCAT attenuation than polychromatic CT. PCAT attenuation assessed by CT_{40 keV} may provide a novel imaging marker of plaque vulnerability.